Methods of enrichment of minerals. Classification of methods and processes of enrichment Enrichment of minerals application of physics
Preparatory processes for mineral processing
Introduction
Purpose of mineral processing
The mined rock mass is a mixture of pieces of mineral complexes, intergrowths of minerals with different physical, physicochemical and chemical properties. To obtain final products (concentrates of metals, coke, building materials, chemical fertilizers, etc.), it must be subjected to a number of processing processes: mechanical, thermal, chemical.
The processing of minerals at the concentrator includes a number of operations, as a result of which the separation of useful components from impurities is achieved, those. bringing the mineral to a quality suitable for subsequent processing, for example, it is necessary to increase the content of: iron from 30-50% to 60-70%; manganese from 15-25% to 35-45%, copper from 0.5-1.5% to 45-60%, tungsten from 0.02-0.1% to 60-65%.
According to their purpose, the processes of processing minerals are divided into preparatory, main(enrichment) and support.
Preparatory processes are designed to open or open grains of useful components (minerals) that make up minerals, and dividing them into size classes, meeting the technological requirements of subsequent enrichment processes.
The preparatory processes include crushing, grinding, screening and classification.
Enrichment of minerals is a set of processes of mechanical processing of mineral raw materials, which makes it possible to separate useful minerals (concentrate) from waste rock.
Concentration engineers should solve the following tasks:
Integrated development of mineral resources;
Utilization of processed products;
Creation of new processes of non-waste technology for separating minerals into final marketable products for their use in industry;
Environmental protection.
Separation of mixtures of minerals is carried out on the basis of differences in physical, physico-chemical and chemical properties to obtain a number of products with a high content of valuable components (concentrates) , low (intermediate products) and insignificant (waste, tailings) .
The enrichment process is aimed not only at increasing the content of a valuable component in the concentrate, but also at removing harmful impurities:
sulfur in the corner phosphorus in manganese concentrate, arsenic in brown iron ore and sulfide polymetallic ores. These impurities, getting into cast iron and then into steel, worsen the mechanical. metal properties.
Brief information about minerals
minerals called ores, non-metallic and combustible fossil materials used in industrial production in natural or processed form.
To ores include minerals that contain valuable components in an amount sufficient to make their extraction economically viable.
Ores are classified into metallic and non-metallic.
metal ores- raw materials for the production of ferrous, non-ferrous, rare, precious and other metals - tungsten-molybdenum, lead-zinc, manganese, iron, cobalt, nickel, chromite, gold-containing;
non-metallic ores- asbestos, barite, apatite, phosphorite, graphite, talc, antimony, etc.
Nonmetallic minerals - raw materials for the production of building materials (sand, clay, gravel, building stone, Portland cement, building gypsum, limestone, etc.)
combustible minerals - solid fuel, oil and combustible gas.
Minerals consist of minerals that differ in their value, physical and chemical properties (hardness, density, magnetic permeability, wettability, electrical conductivity, radioactivity, etc.).
Minerals- called native (i.e. occurring in nature in its pure form) elements and natural chemical compounds.
Useful mineral (or component)- they call an element or its natural compound, in order to obtain which the extraction and processing of a mineral is carried out. For example: in iron ore, useful minerals are magnetite Fe 3 O 4, hematite Fe 2 O 3.
Useful impurities- called minerals (elements), the content of which in small quantities leads to an improvement in the quality of products obtained from useful minerals. For example, impurities vanadium, tungsten, manganese, chromium in iron ore positively affect the quality of the metal smelted from it.
Harmful impurities- called minerals (elements), the content of which in small quantities leads to a deterioration in the quality of products obtained from useful minerals. For example, impurities sulfur, phosphorus, arsenic adversely affect the steelmaking process.
Companion elements called the components contained in the mineral in small quantities, released during the enrichment process into individual products or the product of the main component. Further metallurgical or chemical processing of satellite elements allows them to be extracted into a separate product.
Minerals of waste rock- call components that do not have industrial value. In iron ore, these may include SiO 2 , Al 2 O 3 .
Depending on the structure, minerals are distinguished interspersed and solid, for example, in disseminated - individual small grains of a useful mineral are scattered among grains of waste rock; in solid - grains of a useful mineral are represented mainly by a continuous mass, and minerals of waste rock in the form of interlayers, inclusions.
Enrichment of minerals is a set of technological processes of pre-treatment of mineral raw materials in order to give it qualities that meet the requirements of consumers.
For enrichment:
The content of the useful component in the raw material increases,
Harmful impurities are removed from raw materials,
Uniformity of raw materials in size and composition is achieved.
As a result of enrichment, you get:
Concentrate is a beneficiation product that has a higher content of a useful component compared to ore. According to its content, according to the content of impurities, moisture, concentrates must meet the requirements of GOSTs, OSTs, TUs;
Waste tailings are enrichment wastes consisting of waste rock with a low content of useful components, the extraction of which is technologically impossible or economically unprofitable.
Enrichment reduces the cost of transporting raw materials, as well as its processing, because. a large volume of waste rock is removed.
As a result of enrichment, the content of useful components (%) increases significantly:
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The figure shows the dependence of the specific energy consumption during crushing and grinding of medium-strength material on various final fineness.
The degree of crushing (grinding) is the ratio of the diameter of the largest pieces of ore (D) to the diameter of the pieces of the crushed product (d):
Depending on the properties of the ore, it is used:
1 - crushing - destruction as a result of compression of pieces between two pressing bodies;
2 - splitting - destruction as a result of wedging between the tips of crushing bodies;
3 - impact - destruction under the action of short-term dynamic loads;
4 - abrasion - destruction as a result of the action of surfaces moving relative to each other.
Depending on the method and mechanism of destruction of pieces of ore, there are:
Jaw crushers (crush and split pieces between periodically approaching plates - cheeks) - devices of periodic action: ore crushing alternates with an unloading-loading cycle, which is the main disadvantage of this type of crushers, which reduces their productivity;
Cone crushers (crush and abrade pieces between moving and stationary cones) - continuous crushers;
Roll crushers (crush and split pieces between two smooth or toothed shafts moving towards each other) - continuous crushers;
Impact crushers are used to crush soft and viscous materials.
Grinding of the material is carried out in mills of various types:
Drum mills are used to grind material to a particle size of 1-2 mm. This is a steel drum into which grinding bodies are loaded together with ore. Depending on the type of crushing bodies, there are ball, rod, pebble and self-grinding mills.
After each stage of crushing (grinding), a fine fraction is separated from the resulting product by screening (sifting). Screening is usually used to separate materials with a particle size above 1-2 mm.
Hydraulic classification methods are used to separate materials with a particle size of less than 100 microns. Hydraulic classification is the process of separating a mixture of mineral grains by size based on differences in their settling rates in water.
Then comes the enrichment itself. The most common enrichment methods are:
flotation,
Gravitational,
Magnetic,
Electric.
Via flotation more than 90% of all ores of ferrous and non-ferrous metals are enriched, as well as non-metallic minerals: sulfur, graphite, phosphate ores, coal.
The flotation system is heterogeneous and includes three phases: solid, liquid, gas. Flotation is based on the ability of solid particles to be held at the interface between the liquid and gas phases, i.e. on hydrophobicity, impermeability of particles. Froth flotation is the most common. Mineral grains that are not wetted by water stick to air bubbles and float to the surface. By changing the flotation conditions, for example, the following can be achieved: during the flotation of iron ores, magnetite (iron ore concentrate) will be released into the froth product - direct flotation, and quartz (waste rock) can be released - reverse flotation, i.e. flotation processes are versatile due to the variety of methods of conducting and wide control possibilities.
To conduct the flotation process, it is necessary to use various chemical compounds:
Collectors - dramatically increase the hydrophobicity of the surface of the extracted particles. When flotation of sulfide materials is used
R-O-C-S-Me xanthates and RO S dithiophosphates
(R is an alcohol or phenol radical; Me is Na or K);
Non-sulfide minerals are floated with Na-soaps of fatty acids (Na oleate - С17Н33СООНa) or amines (RNH2);
Coal, sulfur and other naturally hydrophobic minerals are floated using kerosene and other non-polar reagents.
Blowing agents - substances that facilitate the dispersion of air, prevent the merging of bubbles and increase the strength of the foam (various surfactants, pine oil);
Environment regulators - create the optimal pH of the environment (lime, soda, sulfuric acid).
The flotation process is carried out in flotation machines. The foam product is fed to dehydration.
Gravity processes are based on the difference in the nature and speed of movement of mineral particles with different densities in an aqueous or air environment:
Washing - separation by loosening and removing clay materials with the help of water, which hold the grains of minerals (iron and manganese ores, phosphorites, placers of non-ferrous, rare and precious metals, washing of golden sand, high-quality building material);
Enrichment in heavy environments– division of mined minerals by density. The resulting products (heavy and light fractions) have a density greater or less than the density of the separating medium and because of this either float or sink in it. Such enrichment is the main thing in the coal industry. Organic liquids, aqueous solutions of salts and suspensions are used as heavy media:
Organic liquids: trichloroethane C2H3C13 (density 1460 kg/m3), chloroform CC14 (1600), dibromoethane C2H4Br2 (2170), acetylenetetrabromide C2H1Br2 (2930);
Aqueous solutions of inorganic salts: CaCd2 (1654), ZnC12 (2070);
Suspensions: various substances crushed to less than 0.1 mm are used as weighting agents - clay (1490), pyrite (2500), galena PbS (3300). When enriching coal, a suspension of magnetite (2500) is used.
Magnetic enrichment used in the processing of ores of ferrous, rare and non-ferrous metals. It is based on the use of differences in the magnetic properties of minerals and waste rock. When particles move through a magnetic field, magnetic and non-magnetic products move along different trajectories. According to the specific magnetic susceptibility, minerals are divided into:
Strongly magnetic - magnetite Fe 3 O 4, pyrrhotite Fe 1-n S n - χ\u003e 380 * 10 -7 m3 / kg,
Weakly magnetic - hydroxides and carbonates of Fe and Mn - χ \u003d (7.5-1.2) * 10-7 m3 / kg,
Non-magnetic quartz SiO2, apatite Ca5(F,Cl)(PO4)3, rutile TiO2, feldspar (Na,K,Ca)(AlSi3O8).
Electrical enrichment is based on the different electrical conductivity of rocks and their properties to be electrified. Electrical separation is used to enrich granular bulk solids with a particle size of 0.05-3 mm, the components of which do not have significant differences in other properties (density, magnetic susceptibility, physical and chemical properties of the surface).
Depending on the specific electrical conductivity, minerals are divided into:
Conductors - rutile, pyrite,
Semiconductors - magnetite,
Non-conductors - quartz, zircon (ZrSO4).
When the particles of the mineral-conductor come into contact with the electrode, they are charged with the same charge. The dielectric particle is not charged in this case. The particles then pass through a constant electric field and change their trajectories depending on the charge on their surface.
Concentrators are a source of significant dust and wastewater emissions.
Dust formation occurs during the processing and storage of solid mineral raw materials. Strong dust emission is observed during dry crushing, screening, with dry enrichment methods, transportation and reloading of enrichment products.
During the operation of crushers, the main dust emission occurs in the places of product unloading and reaches 4 g/s for roller crushers, 10 g/s for cone and jaw crushers, and 120 g/s for hammer crushers. During the operation of the mills, up to 80 g/s of dust is released.
Wastewater is discharged into tailings along with enrichment tailings, from where it can enter water bodies.
The main pollutants are coarse impurities (gravitational enrichment tailings), salts in dissolved form, flotation reagents in the form of emulsions, products of the interaction of reagents with each other and with minerals.
Wastewater may contain:
Acids used in the technological process
Ions of Fe, Cu, Ni, Zn, Pb, Al, Co, Cd, Sb, Hg and others that enter wastewater due to the dissolution of their compounds by acids,
Cyanides are the main pollutant of gold recovery plants and factories that use cyanide melt as a flotation reagent,
Fluorides, if the flotation reagents are NaF, NaSiF6,
Petroleum products, most often - kerosene, flotation agent in the enrichment of coal, sulfur, Cu-Mo, Mo-W rudB
Phenols as flotation agents, xanthates and dithiophosphates are flotation agents with an unpleasant odor.
Some minerals mined from the bowels of the earth are directly used in certain sectors of the national economy (stone, clay, limestone for construction purposes, mica for electrical insulation, etc.), but most of them are preliminarily enriched.
Enrichment of minerals called a set of operations of mechanical processing of a mineral in order to obtain products suitable for use in the national economy.
The process of enrichment of minerals is carried out at specially equipped, highly mechanized enterprises. These businesses are called processing plants if their main task is to separate minerals and crushing and screening plants, if enrichment is reduced mainly to crushing rocks and separating them by size and strength.
Minerals at processing plants undergo a series of sequential operations, as a result, useful components are separated from impurities. Mineral enrichment processes according to their purpose are divided into preparatory, basic and auxiliary .
To preparatory include the processes of crushing, grinding, screening and classification. Their task is to bring the mineral components into a state in which it is possible to conduct separation (decrease in size, separation by size, etc.);
To the main include the following processes:
gravity;
flotation;
magnetic;
electrical;
special;
combined.
The task of the main enrichment processes is to separate the useful mineral and waste rock.
to auxiliary include dehydration, dust collection, wastewater treatment, testing, control and automation, unloading, dry and water transport of material, mixing, distribution of material and reagents to machines, etc.
The task of these processes is to ensure the optimal flow of the main processes.
The set of sequential technological processing operations that minerals are subjected to at processing plants is called enrichment scheme. Depending on the nature of the information contained in the enrichment scheme, it is called technological, qualitative, quantitative, qualitative-quantitative, water-slurry and apparatus circuit diagram.
Everything that enters the enrichment or a separate enrichment operation is called source material, or nutrition.
The source material for the processing plant is ore. The percentage of a valuable component in the source material (ore) is usually denoted by (alpha). Products enrichment (or operation) refers to the materials obtained as a result of enrichment - concentrate, intermediate product (middle product) and tailings.
Concentrate the product of enrichment is called, in which the content of the valuable component is greater than in the original material. The percentage of the valuable component in the concentrate is denoted by (beta).
Tails called a beneficiation product that has a low content of a valuable component compared to the original ore. The percentage of a valuable component in the tails is usually denoted by (theta). Tailings are mainly waste rock and harmful impurities.
intermediate product(middle product) is a product in which the content of the valuable component is less than in the concentrate, and more than in the tails. The content of a valuable component in it is denoted by . Industrial products are usually sent for additional processing.
Concentrates and tailings can be both products of separate operations and final products of the enrichment process. The quality of the final or so-called commodity concentrates must comply with the state standard (GOST). Each GOST provides for the minimum content of a valuable component in concentrates and the permissible content of impurities.
To evaluate the enrichment results, the following main technological indicators and their symbols are used:
Output(gamma) - the amount of the product obtained, expressed as a percentage (or fractions of a unit) of the starting material.
The output of concentrate, middlings, tailings is determined from the following expressions:
where C is the amount of concentrate;
M - the amount of processed ore;
P - the amount of middlings.
Degree of extraction e(epsilon) - expressed as a percentage, the ratio of the amount of a valuable component in a given product (usually in a concentrate) to its amount in the source material (ore), taken as 100%. The degree of extraction into concentrate, middlings, tailings is determined from the formulas:
Degree of concentration(or enrichment factor) K - the ratio of the content of a valuable component in the concentrate to its content in the source material (ore):
Often the mass of products is unknown. But the content of a useful component in products is almost always known.
The yield of concentrate and tailings, its extraction are determined through the content by the following formulas:
According to such formulas, in the process of working at factories, it is possible to evaluate enrichment, having only data on the chemical analysis of ore () and enrichment products ( , ). In a similar way, equations and formulas can be obtained for the case when two concentrates and tails are obtained in the enrichment process, i.e., for two valuable components.
These equations are different expressions of the general rule that that the amount of material supplied for enrichment is equal to the sum of the products obtained
The rock mass is subdivided into: main (actually concentrating); preparatory and auxiliary.
All existing enrichment methods are based on differences in the physical or physico-chemical properties of individual components of a mineral. There are, for example, gravitational, magnetic, electrical, flotation, bacterial and other methods of enrichment.
Technological effect of enrichment
Preliminary enrichment of minerals allows:
- to increase the industrial reserves of mineral raw materials through the use of deposits of poor minerals with a low content of useful components;
- increase labor productivity at mining enterprises and reduce the cost of mined ore due to the mechanization of mining operations and the continuous extraction of minerals instead of selective;
- to improve the technical and economic indicators of metallurgical and chemical enterprises in the processing of enriched raw materials by reducing the cost of fuel, electricity, fluxes, chemical reagents, improving the quality of finished products and reducing the loss of useful components with waste;
- to carry out the complex use of minerals, because preliminary enrichment makes it possible to extract from them not only the main useful components, but also accompanying ones, which are contained in small quantities;
- reduce the cost of transporting mining products to consumers by transporting richer products, and not the entire volume of mined rock mass containing minerals;
- isolate harmful impurities from mineral raw materials, which, during their further processing, can degrade the quality of the final product, pollute the environment and threaten human health.
Processing of minerals is carried out at processing plants, which today are powerful highly mechanized enterprises with complex technological processes.
Classification of enrichment processes
The processing of minerals at processing plants includes a series of sequential operations, as a result of which the separation of useful components from impurities is achieved. According to their purpose, the processes of processing minerals are divided into preparatory, main (enrichment) and auxiliary (final).
Preparatory processes
Preparatory processes are designed to open or open the grains of useful components (minerals) that make up the mineral and divide it into size classes that meet the technological requirements of subsequent enrichment processes. The preparatory processes include crushing, grinding, screening and classification.
Crushing and grinding
Crushing and grinding- the process of destruction and reduction in the size of pieces of mineral raw materials (minerals) under the action of external mechanical, thermal, electrical forces aimed at overcoming the internal cohesive forces that bind the particles of a solid body together.
According to the physics of the process, there is no fundamental difference between crushing and grinding. Conventionally, it is considered that when crushing, particles larger than 5 mm are obtained, and when crushed, particles are smaller than 5 mm. The size of the largest grains to which it is necessary to crush or grind a mineral during its preparation for enrichment depends on the size of the inclusions of the main components that make up the mineral and on the technical capabilities of the equipment on which the next operation of processing the crushed (crushed) product is supposed to be carried out .
Opening grains of useful components - crushing and (and) grinding of intergrowths until the grains of a useful component are completely released and a mechanical mixture of grains of a useful component and waste rock (mix) is obtained. Opening grains of useful components - crushing and (and) grinding of intergrowths until part of the surface of the useful component is released, which provides access to the reagent.
Crushing is carried out on special crushing plants. Crushing is the process of destruction of solids with a decrease in the size of the pieces to a given fineness, by the action of external forces that overcome the internal cohesive forces that bind the particles of the solid. Grinding of crushed material is carried out in special mills (usually ball or rod).
Screening and classification
Screening and classification are used to separate a mineral into products of different sizes - size classes. Screening is carried out by screening the mineral on a sieve and sieves with calibrated holes into a small (under-screen) product and a large (over-screen) product. Screening is used to separate minerals by size on screening (screening) surfaces, with hole sizes from a millimeter to several hundred millimeters.
Screening is carried out by special machines - screens.
Minerals, the components of which have differences in electrical conductivity or have the ability, under the influence of certain factors, to acquire electrical charges of different magnitude and sign, can be enriched by the method of electrical separation. Such minerals include apatite, tungsten, tin and other ores.
Enrichment by fineness is used in cases where useful components are represented by larger or, conversely, smaller grains in comparison with grains of waste rock. In placers, useful components are in the form of small particles, so the separation of large classes allows you to get rid of a significant part of rock impurities.
Differences in grain shape and friction coefficient make it possible to separate flat, scaly particles of mica or fibrous asbestos aggregates from rock particles that have a rounded shape. When moving along an inclined plane, fibrous and flat particles slide, and rounded grains roll down. The rolling friction coefficient is always less than the sliding friction coefficient, so flat and rounded particles move along an inclined plane at different speeds and along different trajectories, which creates conditions for their separation.
Differences in the optical properties of the components are used in the enrichment of minerals by the method of photometric separation. This method is used to mechanically separate grains of different colors and luster (for example, separating diamond grains from waste rock grains).
The main final operations are pulp thickening, dehydration and drying of enrichment products. The choice of dewatering method depends on the characteristics of the material to be dewatered (initial moisture content, particle size distribution and mineralogical composition) and final moisture requirements. It is often difficult to achieve the required final moisture in one stage, therefore, in practice, for some enrichment products, dehydration operations are used in various ways in several stages.
Waste
Waste - end products of enrichment with a low content of valuable components, the further extraction of which is technically impossible and / or economically inexpedient. (This term is equivalent to the previously used term tailings, but not the term tails, which, in contrast to waste, is the depleted product of any single enrichment operation).
Intermediates
Intermediate products (middle products) are a mechanical mixture of intergrowths with open grains of useful components and waste rock. Intermediates are characterized by a lower content of useful components in comparison with concentrates and a higher content of useful components in comparison with waste.
Enrichment quality
The quality of minerals and enrichment products is determined by the content and extraction of a valuable component, impurities, related elements, as well as moisture content and fineness.
Mineral processing is ideal
Under the ideal enrichment of minerals (ideal separation) is understood the process of separation of the mineral mixture into components, in which there is no clogging of each product with particles foreign to it. The efficiency of ideal mineral processing is 100% by any criteria.
Partial mineral processing
Partial enrichment is the enrichment of a separate class of mineral size, or the separation of the most easily separated part of contaminating impurities from the final product in order to increase the concentration of a useful component in it. It is used, for example, to reduce the ash content of unclassified thermal coal by separating and enriching a large class with further mixing of the resulting concentrate and fine unenriched screenings.
Losses of minerals during enrichment
The loss of a mineral during enrichment is understood as the amount of a useful component suitable for enrichment, which is lost with enrichment waste due to process imperfections or violations of the technological regime.
Permissible norms for intercontamination of enrichment products for various technological processes, in particular, for coal enrichment, have been established. The allowable percentage of mineral losses is removed from the balance of enrichment products to cover discrepancies when taking into account the mass of moisture, the removal of minerals with flue gases from dryers, and mechanical losses.
Mineral Processing Boundary
The boundary of mineral processing is the smallest and largest size of particles of ore, coal, effectively enriched in the processing machine.
Depth of enrichment
The depth of enrichment is the lower limit of the fineness of the material to be enriched.
When enriching coal, technological schemes are used with enrichment limits 13; 6; one; 0.5 and 0 mm. Accordingly, unenriched screenings with a particle size of 0-13 or 0-6 mm, or sludge with a particle size of 0-1 or 0-0.5 mm are allocated. An enrichment limit of 0 mm means that all size classes are subject to enrichment.
International congresses
Since 1952, International Mineral Processing Congresses have been held. Below is a list of them.
| Congress | Year | Location |
|---|---|---|
| I | 1952 | London |
| II | 1953 | Paris |
| III | 1954 | Goslar |
| IV | 1955 | Stockholm |
| V | 1960 | London |
| VI | 1963 | Caen |
| VII | 1964 | New York |
| VIII | 1968 | Leningrad |
| IX | 1970 | Prague |
| X | 1973 | London |
| XI | 1975 | Cagliari |
| XII | 1975 | Sao Paulo |
| XIII | 1979 | Warsaw |
| XIV | 1982 | Toronto |
| XV | 1985 | Caen |
| XVI | 1988 | Stockholm |
| XVII | 1991 | Dresden |
| XVIII | 1993 | Sydney |
| XIX | 1995 |
(lecture notes)
V.B.Kuskov
SAINT PETERSBURG
CONTROL 2
1. preparatory processes 8
1.1. GRANULOMETRIC COMPOSITION 8
1.2 CRUSHING 10
1.3. screening 14
1.4. GRINDING 17
1.5. HYDRAULIC CLASSIFICATION 20
2. MAIN PROCESSES OF ENRICHMENT 23
2.1. GRAVITATIONAL ENRICHMENT METHOD 23
2.3. MAGNETIC ENRICHMENT METHOD 35
2.4. ELECTRIC ENRICHMENT 39
2.5. special ENRICHMENT METHODS 43
2.6. COMBINED ENRICHMENT METHODS 48
3 AUXILIARY ENRICHMENT PROCESSES 49
3.1. DEHYDRATION OF ENHANCEMENT PRODUCTS 49
3.2. DUST EXTRACTION 53
3.3. WASTEWATER TREATMENT 54
3.3 TESTING, CONTROL AND AUTOMATION 55
4. BENEFITS 55
Doing
Minerals- natural mineral formations of the earth's crust, the chemical composition and physical properties of which allow them to be effectively used in the sphere of material production. Field mineral - an accumulation of mineral matter in the bowels or on the surface of the Earth, in terms of quantity, quality and conditions of occurrence suitable for industrial use. (With large areas of distribution, deposits form districts, provinces and basins). There are solid, liquid and gaseous minerals.
Solid minerals (ores), in turn, are divided into combustible (peat, shale, coal) and non-combustible, which are: agronomic (apatite and phosphorite, etc.), non-metallic (quartz, barite, etc.) and metallic (ores ferrous and non-ferrous metals). The efficiency of using one or another mineral depends, first of all, on the content of a valuable component in it and the presence of harmful impurities. Direct metallurgical or chemical processing of a mineral is expedient (technically and economically profitable) only if the content of the useful component in it is not lower than a certain limit determined by the level of development of engineering and technology (and the need for this raw material) at the present time. In most cases, the direct use of the mined rock mass or its processing (metallurgical, chemical, etc.) is not economically feasible, and sometimes technically impossible, because. minerals suitable for direct processing are rare in nature; in most cases, they are subjected to special processing - enrichment.
Mineral enrichment a set of processes of mechanical processing of mineral raw materials in order to extract useful (valuable) components and remove waste rock and harmful impurities. As a result of enrichment, concentrate (concentrates) and tailings are obtained from ore.
Concentrate- this is a product where most of the useful minerals (and a small amount of waste rock minerals) are released (concentrated). The quality of the concentrate is mainly characterized by the content of the valuable component ( it is always higher than in ore, the concentrate is richer in the valuable component (hence the name - enrichment), as well as in the content of useful and harmful impurities, humidity and granulometric characteristics.
Tails- a product into which most of the waste rock minerals, harmful impurities and an insignificant amount of a useful component will be released (the content of valuable components in tailings is lower than in concentrates and ore).
In addition to concentrate and tailings, it is possible to obtain intermediate products, i.e. products characterized by a lower content of useful components compared to concentrates and a higher content of useful components compared to tailings.
Useful(valuable) components are called chemical elements or natural compounds, for the production of which this mineral is mined and processed. As a rule, the valuable component in the ore is in the form of a mineral (there are few native elements in nature: copper, gold, silver, platinum, sulfur, graphite).
Useful impurities name chemical elements or natural compounds that are part of the mineral in small quantities and improve the quality of the finished product (or are released during further processing). For example, useful impurities in iron ores are alloying additives such as chromium, tungsten, vanadium, manganese, etc.
Harmful impurities name individual elements and natural chemical compounds contained in minerals in small quantities and having a negative impact on the quality of finished products. For example, harmful impurities in iron ores are sulfur, arsenic, phosphorus, in coking coals - sulfur, phosphorus, in thermal coals - sulfur, etc.
Enrichment of minerals allows you to increase economic efficiency of their further processing, also, in some cases, without the enrichment stage, further processing becomes generally impossible. For example, copper ores (containing, as a rule, very little copper) cannot be directly smelted into metallic copper, since copper passes into slag during smelting. In addition, enrichment of minerals allows you to:
increase industrial stocks of raw materials through the use of deposits of poor minerals with a low content of valuable components;
increase labor productivity at mining enterprises and reduce the cost of mined ore due to the mechanization of mining operations and continuous extraction of minerals instead of selective;
integrated use of minerals, since preliminary enrichment allows extracting not only the main useful components, but also accompanying ones contained in small quantities;
reduce the cost of transporting richer products to consumers, rather than the entire volume of extracted minerals;
extract from mineral raw materials those harmful impurities that, during its further processing, can pollute the environment and thereby threaten human health and worsen the quality of the final product.
Enrichment methods can also be used in the processing of municipal solid waste (350-400 kg/year per person are generated).
Minerals at processing plants undergo a series of sequential operations, as a result of which useful components are separated from impurities. Processes of mineral processing according to their purpose are divided into preparatory, auxiliary and main ones.
To preparatory include the processes of crushing, grinding, screening and classification. Their task is to separate the useful mineral and the waste rock (“open” the intergrowths) and create the desired granulometric characteristic of the processed raw material.
Task major beneficiation processes - to separate useful mineral and waste rock. To separate minerals, differences in the physical properties of the separated minerals are used. These include:
|
Name of enrichment method |
Physical properties used for separation |
The main types of minerals enriched by this method |
|
Gravitational enrichment method |
Density (taking into account size and shape) |
Coals (+1 mm), slates, gold-bearing, tin ores… |
|
Flotation enrichment method |
Surface wettability |
Ores of non-ferrous metals, apatite, phosphorite, fluorite ores... |
|
Magnetic enrichment method |
Specific magnetic susceptibility |
Iron ore... |
|
Electric enrichment method |
Electrical properties (electrical conductivity, tribocharge, permittivity, pyrocharge) |
Fine-tuning of diamond ores, rare metal: titanium-zirconium, tantalum-niobium, tin-tungsten, rare earth (monazite-xenotime). Glass sands, electronic scrap… |
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Ore sorting: Mining Radiometric enrichment |
External signs: color, luster, shape The ability of particles to emit, reflect, absorb various types of energy |
Precious stones, sheet mica, long-fiber asbestos Ores of ferrous and non-ferrous metals, diamond-bearing, fluorite and other ores |
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selective crushing |
Strength difference |
Phosphorite ores, coals and slates |
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Enrichment in form | ||
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Combined Methods |
In addition to traditional enrichment processes (which do not affect the chemical composition of raw materials), the scheme includes pyro- or hydrometallurgical operations that change the chemical composition of raw materials. |
Uranium, gold-bearing (primary) ores, copper-nickel ores… |
In addition to the above, there are other enrichment methods. Also, sometimes agglomeration processes (increasing the size of materials) are referred to enrichment processes.
To auxiliary include dewatering, dust collection, wastewater treatment, sampling, control and automation. The task of these processes is to ensure the optimal flow of the main processes, to bring the separation products to the required conditions.
The set of sequential technological processing operations that minerals are subjected to at processing plants is called enrichment scheme. Depending on the nature of the information contained in the enrichment scheme, it is called technological, qualitative, quantitative, qualitative-quantitative, water-slurry and apparatus circuit diagram.
Enrichment, like any other technological process, is characterized by indicators. The main technological indicators of enrichment are as follows:
Q mass of the product (productivity); P – mass (capacity) of the calculated component in the product . They are usually expressed in tons per hour, tons per day, etc.;
the content of the calculated component in the product - , is the ratio of the mass of the calculated component in the product to the mass of the product; the content of various components in a mineral and in the resulting products is usually calculated as a percentage (sometimes the content in the source material is denoted by , in concentrate - , in tailings - ). The content of useful components in the extracted raw material (ore) can range from fractions of a percent (copper, nickel, cobalt, etc.) to several percent (lead, zinc, etc.) and several tens of percent (iron, manganese, fossil coal and some other non-metallic minerals);
product yield – i, k, xv is the ratio of the mass of the product to the mass of the original ore; the yield of any enrichment product is expressed as a percentage, less often in fractions of a unit;
Extraction of a valuable component – u, k, xv is the ratio of the mass of the calculated component in the product to the mass of the same component in the original ore; extraction is expressed as a percentage, less often in fractions of a unit.
Output i-th product is calculated by the formula:
i = (Q i /Q ref)100,%
Also, for the case of separation into two products - concentrate and tailings, their yield can be determined through the content using the following formulas:
k = 100,%; xv = 
100,%;
The sum of concentrate and tailings yields is:
k + xv = 100%.
It's obvious that
Q con + Q xv = Q ref.;
R con + R xv = R ref.
1 + 2 +…+ n = 100%.
Similarly for Q and R.
(In mineral processing, as a rule, only two products are obtained - concentrate and tailings, but not always, sometimes there can be more products).
.
In practice, the contents are usually determined by chemical analysis.
Extracting a useful component in i– th product:
i
=
100.%, or i = 
%.
The sum of concentrate and tailings extractions is equal to:
to + xv = 100%.
This formula is valid for any number of products:
1 + 2 +… n = 100%.
To find the content in the product of mixing, you can use the so-called balance equation (for the case of separation into two products):
to con + xv con = ref ref.
The equation is also valid for any number of products:
1 1 + 2 2 +…+ n n = ref ref.
It should be noted that ref = 100%.
Example. The ore is separated into two products (Fig. 1.1) - concentrate and tailings. Ore productivity Q ref = 200 t/h, for concentrate - Q con = 50 t/h. Performance by design component R ref = 45 t/h, by component in concentrate R con = 40 t/h.
Q xv = Q ref - Q con \u003d 200 - 50 \u003d 150 t / h;
con = ( Q con / Q ref)100 = (50/200)100 = 25%;
xv \u003d ref - k \u003d 100 - 25 \u003d 75%,
or xv = ( Q xv / Q ref)100 =(150/200) . 100=75%;
it's obvious that Q xv = ( xv Q ref)/100 = (75200)/100 = 150 t/h;
=
=
=
22,5 %;
=
=
=
80 %;
R xv = R ref - R con \u003d 45 - 40 \u003d 5,
then 
=
=
=3,33 %.
Or using the balance equation we have:
to con + xv con = ref ref,
xv = 
=
=
3,33 %.